1. Field of the Invention
The present invention relates to a hand-held apparatus for performing medical calculations. Particularly, the present invention is directed to a compact, self-contained apparatus capable of performing medical calculations accurately by prompting and validating data entries, as well as identifying relevant measurements from graphical information such as electrocardiogram waveforms.
2. Description of Related Art
Nurses and health care professionals are responsible for accurately providing a variety of calculations and measurements to assist in the treatment of patients. In addition to continuously monitoring and recording the body functions of a patient, such as pulse and blood pressure, these health care professionals must also calculate and convert prescriptions into the appropriate dosage of medication available to satisfy the size and age of the patient, as well as interpret laboratory results to determine Arterial Blood Gases (ABGs) and other conditions. These medical calculations typically are performed bedside, often in a stressful or difficult environment.
With regard to cardiac care patients, an additional duty of the health care professional is to inspect ECG/EKG waveforms that are printed from a bedside cardiac monitor. For example, the health care professional typically obtains a six-second rhythm strip from the bedside monitor and measures various intervals along the waveform printed on the rhythm strip that reflect the current cardiac status of the patient. If the measured value falls outside of a predetermined range, the health care professional must then contact the responsible physician to order more extensive testing using twelve-lead ECG diagnostic machines. Unlike the bedside cardiac monitors, these twelve-lead ECG diagnostic machines are more complex and expensive to operate.
To perform these responsibilities, the health care professional currently must rely on a variety of tools or equipment. Such equipment includes a clock, a stop watch, nomograms, charts, formulae, a calculator and a pair of calipers. Because the health care professional must constantly be on his or her feet, it is difficult to ensure that these tools will be readily accessible when needed. Additionally, the health care professional must often rely on memory rather than carrying charts and books of formulae.
In making these calculations and measurements, a simple mistake could prove to be life threatening. Accuracy is crucial. Therefore, it is important that the health care professional verify his or her calculations and measurements, and maintain thorough records. Due to the stressful environment associated with emergency situations, as well as the long and difficult hours typically required in the health care profession, there often is not an opportunity verify such calculations. Accuracy also is impaired when the health care professional must rely on his or her eyesight to read and interpret nomograms and ECG/EKG waveforms.
Several apparatus have been developed to assist health care professionals in performing and recording medical calculations. For example, U.S. Pat. No. 3,940,742 issued to Hudspeth et al. discloses a portable data acquisition device used for transferring various patient parameters to a printer. U.S. Pat. No. 4,591,974 to Dornbush et al. is directed to an information recording and retrieval system, which includes a number of hand held computers in communication with a host computer. Each hand held computer is used for entering medical data in a preprogrammed tabular format for subsequent transfer to and manipulation by the host microcomputer. The portable handheld terminal of the U.S. Pat. No. 4,916,441, issued to Gombrich, likewise is provided in communication via a local area network with a central file server for access to documented patient information, test results and physician orders, as well as for bedside data input using preprogrammed bar code entries.
With regard to graphical information, U.S. Pat. No. 5,111,396 to Mills et al. discloses a portable ECG data-storage apparatus for the capture, storage and playback of selective "windows" of successive plural-lead ECG data records. This is performed by connecting the apparatus to a conventional ECG machine, and then converting the captured analog signals into digital data for subsequent storage and playback. A risk management system is disclosed by U.S. Pat. No. 5,276,612 to Selker, which receives waveform signals from a conventional ECG machine and generates characteristic values for use by a predictive instrument.
Although these various devices are beneficial in the health care profession, each requires communication with a larger host computer or similar base equipment. The use of such a network of equipment is generally complex to operate and expensive to purchase and maintain. A few self-contained apparatus have been developed, such as the self-contained minicomputer for calculating and converting between known medical units disclosed by U.S. Pat. No. 4,290,113 to Haker et al. and the self-contained portable monitoring apparatus disclosed by U.S. Pat. No. 5,050,612 to Matsumura. However, these devices only offer a few limited functions. Additionally, there is no known manner of validating data entry for accuracy.
In view of the above, there remains a need for a self-contained, hand-held apparatus capable of accurately performing medical calculations. Particularly, there remains a need for a hand-held apparatus that allows simple selection and execution of a desired medical calculation, and validates proper entry of required data to ensure accuracy. There likewise remains a need for a hand-held apparatus that easily and accurately calculates relevant measurements from graphical information, such as electrocardiogram waveforms.